The synthesis and photophysical properties of halide sensitive acridizinium dyes

A series of acridizinium (benzo[b]quinolizinium) salts containing methoxy, fluoro and chloro substituents were synthesized and their spectroscopic properties and sensitivity towards halide quenching in water were determined. The salts have substantially improved properties over the commonly employed quinolinium and acridinium fluorophores for the sensing of bromide and iodide ions. Of the substituted acridiziniums investigated, 8,10-difluoro-acridizinium bromide has the best combination of properties as a bromide or iodide sensor.     

Dynamic mechanical properties of polyurethane block polymers

The dynamic mechanical properties of polyester and polyether urethane block polymers have been investigated at four frequencies (3.5, 11, 35 and 110 Hz) in the temperature range of — 150 to 200°C. The existence of a two phase structure was demonstrated in these systems by the observation of two major transition regions corresponding to (1) the glass transition temperature (T_g) of the ester or ether soft segments, and to (2) the softening temperature of the aromatic-urethane hard segments. Several secondary relaxations were observed in addition to the two major relaxations. It was possible to assign molecular mechanisms to each of these relaxations. All relaxation phenomena were greatly influenced by the molecular weight of the prepolymer, weight percent of hard segments, and thermal history. An increase in the molecular weight of the prepolymer above 1,000 at constant hard segment content resulted in a semi-crystalline material, which possessed a lower T_g for the macroglycol segments. Annealing to enhance crystallinity increased the T_g of the soft segments, consistent with the usual observation in semicrystalline homopolymers. These findings suggest that the relaxation mechanisms of polyurethane block polymers are not only influenced by the degree of crystallinity, but also by the nature of the domain structure.     

Preparation and photophysical properties of organic fluorescent polymers and their nanoparticles

New classes of stable organic florescent polymer nanoparticles were prepared from the corresponding tetrahydrofuran (THF) solutions, upon slow evaporation of solvent under a mild vacuum. Uniform spherical nanospheres having mean diameter of ? 500–700 nm, showed enhanced fluorescence emission in solution, but it diminished when it is destroyed using an organic base. These end‐capped fluorescent polymers are highly stabilized in the excited states at higher concentration in solution, leads no more intra‐ and intermolecular interactions among the excited molecules, because of the absence of free functional groups. The significant enhancement in fluorescence emission was attributed to the high level of molecular stacking in the fluorescent nanoparticles, when compared with micron‐sized isolated powder sample. In addition, these fluorescent polymers exhibited significant thermal properties, along with better solubility in most of common organic solvents for their future application. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5344–5350, 2006     

The synthesis,crystal structure and photophysical properties of three novel naphthalimide dyes

Three new naphthalimide derivatives containing an electron-donor moiety (carbazole), 4-carbazolyl-N-methyl-1,8-naphthalimide, 4-carbazolyl-N-cyclohexyl-1,8-naphthalimide and 4-carbazolyl-N-phenyl-1,8-naphthalimide were synthesized and crystal structures confirmed. Crystallographic data revealed that the interplanar angles (θ) of the carbazole and naphthalimide moieties were, respectively, 70.7° and 66.5°. The UV–vis absorption and photoluminescent spectra of the systems in n-hexane, CHCl₃, tetrahydrofuran and CH₂Cl₂ were investigated. The lowest absorption band of the naphthalimide molecular centered at 400–420 nm was assigned to charge-transfer transition with emission at ≈440 nm in n-hexane and at ≈560 nm in CH₂Cl₂.     

Effect of segment size and polydispersity on the properties of polyurethane block polymers

The dynamic-mechanical and thermal scanning behaviour of a series of specially synthesized linear segmented polyurethanes is presented. These materials possess a well defined segment molecular weight and molecular weight distribution and no possibility of intermolecular hydrogen bonding. The dynamic-mechanical transitions observed are assigned to specific molecular motions and the effect of segment size and molecular weight distribution is described. The results are explained in terms of hard segment domain perfection. Differential scanning calorimetry (d.s.c.) curves of annealed samples indicate that domain morphology may be affected by thermal treatment. A comparison of dynamic mechanical and d.s.c. results to hydrogen-bonded polyurethanes is made.     

Dendritic effects on photophysical and fluorescence properties of coumarin functionalized dendrigraft polybutadiene

A series of multicoumarin-functionalized dendrigraft polybutadienes with linear-comb or star-comb topology were synthesized from generation 0 to 3 (LGn and SGn respectively, n = 0–3) to investigate the dendritic effects on photophysical and fluorescence properties. From the results of SEC-TALLS, SEC and ubbelohde viscometer, the polymer architecture converted from one- or two-dimensional structure to a flexible branched structure, then advanced into a compact structure; meanwhile, the LGn exhibited a relatively looser structure than its SGn analog did. Hypsochromic shifts of the absorption and emission maxima, as well as signal amplifications were observed for both LG3 and SG3, suggesting that encapsulation effect occurred at the third generation resulting from the compact architecture. The fluorescence quantum yield (Φ_F) was in the order of LG1 (8.1%) > SG1 (6.4%) > LG2 (5.0%) > SG2 (4.6%) > LG3 (2.3%) > SG3 (2.0%) > SG0 (1.1%) > LG0 (0.7%), indicating that the flexible branched polymer matrix could enhance the fluorescence properties due to the synergistic combination of inter-/intra-molecular fluorescence quenching. Also, the fluorescence properties of polymer with linear-comb architecture were always better than those of star-comb counterpart due to its looser architecture.     

New diaminomaleonitrile-based azo-azomethine dyes; synthesis, characterization and spectral properties

New diaminomaleonitrile-based azo-azomethine dyes were synthesized via a condensation between 2,6-bis(N-(2-amino-1,2-dicyanoetheneimino))-4-methylphenol and 5-(4-substituted-phenyl)-azo-salicyladehyde. FT-IR and ¹H NMR spectroscopy and mass spectrometry studies as well as elemental analysis data revealed the symmetrical bis-iminated structures of the dyes. The electrochemical behavior of the dyes has been investigated by cyclic voltammetry. The effect of various solvents with different polarities on the UV-Vis spectra of the dyes was also studied. The thermal analysis data indicated that the framework of the dyes was stable up to 285 °C.     

Synthesis of branched azo dyes based on benzene sulphonamide intermediates and their spectral properties

Benzene sulphonamide intermediates and two series of branched azo dyes (one series with H‐Acid as the coupling component, and the other, with a pyrazolone derivative as the coupling component) derived from them were synthesised. The molecular structures, spectroscopic properties and dyeing properties of the dyes obtained have been investigated. The results indicated that these dyes showed one dominant hue, despite each separate branch of chromophore, and, in the first series, four chromophoric groups led to only a threefold increase in the extinction coefficient, while the same comparison in the second series produced a fully additive effect, i.e. a fourfold increase. Compared with the mono‐branch dye of each series, the dyeing properties of the H‐Acid series were improved, whereas the pyrazolone series that were run diversely for the two series were synthesised from different coupling components. In addition, the crystallographic structure of the tri‐branch intermediate showed a non‐coplanar structure, which indicated that the derived dye would perform as the sum of three similar chromophoric units.     

Dichroic and spectral properties of anthraquinone-based azo dyes for PVA polarizing film

Dichroic dyes with broad absorption bands are advantageous for the production of neutral gray polarizing films. For this purpose, anthraquinone-based azo dyes were synthesized to have a conjugated bichromophore design and this was applied to PVA polarizing films. The spectral and dichroic properties of the polarizing films were examined and compared to the films produced with a general disazo dichroic dye. The polarizing films with anthraquinone-based azo dyes had wider absorption bands, but lower dichroic ratios compared to the films with a general disazo dichroic dye. It was found that the alignment between the transition moments of the anthraquinone and azo chromophores is an important factor for the dichroic properties of anthraquinone-based azo dyes.     

Synthesis and spectral properties of azohydroxypyridone disperse dyes containing a fluorosulphonyl group

A series of azohydroxypyridone disperse dyes containing fluorosulphonyl groups have been synthesised and their spectral properties were investigated. Azohydroxypyridone dyes, containing a nitro group instead of a fluorosulphonyl group para to the azo group in the diazo component, were also synthesised in order to compare spectral properties. The fluorosulphonyl substituted derivatives absorb maximally at shorter wavelengths and are tinctorially weaker than the nitroarylazopyridone dyes, although the former dyes have higher molar extinction coefficients. Also, the synthesised dyes exhibit positive solvatochromism so that the absorption bands of the dyes move toward longer wavelengths as the polarity of the solvent increases. Molecular computational methods provided reasonable predictions in the direction of solvatochromism for the dyes prepared.     

pH dependent spectral properties and electronic structure of benzothiazol containing cyanine dyes

The absorption and emission properties of some cyanine dyes over a range of 8 pH units are presented. Theoretical investigations of their electronic structure in the ground and excited states have been undertaken and the nature of the electronic transitions in the protonated and non-protonated forms is rationalised.     

Microwave-assisted solvent-free synthesis and spectral properties of some dimethine cyanine dyes as fluorescent dyes for DNA detection

A series of dimethine cyanine dyes were synthesized in a fast, efficient and high yield by the condensation of quaternary salts with 1H-indole-3-carbaldehyde in the presence of piperidine under solvent-free microwave irradiation. The products were identified by ¹H NMR, IR, UV–vis spectroscopy and elemental analysis. The absorption and fluorescence properties of the dyes in both the free state and DNA or BSA were investigated. Significant enhancement of the fluorescent quantum yield was observed for all the dyes in the presence of DNA, with one compound demonstrating excellent sensitivity as a fluorescent probe.     

Surface properties of a segmented polyurethane containing amphiphilic polymers as additives

Two different types of amphiphilic polymers were used as surface-modifying additives to a polyetherurethane, Pellethane 2363–75D, which has T_g close to room temperature. The additives used were a segmented polyetherurethane designated Pol C, and Pluronics PE6800 and PE9400, i.e., triblock copolymers of propylene oxide and ethylene oxide. Pol C was prepared from poly(ethylene glycol), methylene diphenylene diisocyanate, and a fatty acid monoglyceride. The properties of the blends were investigated in their unhydrated state and after water immersion at 23°C and 80°C. Surface composition, water absorption, and leakage of additives to the aqueous phase have been studied. From ESCA and contact angle measurements it was concluded that Pol C was enriched in the surface layer of the matrix material after water immersion at 80°C. The Pluronics showed less effects on the surface properties of the matrix material, probably because of their high water solubility. © 1994 John Wiley & Sons, Inc.     

新型溴代长波长BODIPY类荧光染料的合成及表征

通过吡咯和乙酰氯经一步法合成了含吡咯取代基的长波长BODIPY染料,溴化后得到一溴和二溴染料,染料通过质谱、二维核磁等手段进行了结构表征.测试了这些染料的吸收光谱和发射光谱,研究了不同极性的溶剂对染料光谱性能的溶剂化效应以及Br原子对染料光谱的重原子效应.结果表明:随着溶剂极性的增大所合成的染料吸收波长均发生了蓝移,发射波长变化不大,摩尔消光系数逐渐增大,荧光量子产率逐渐减小,表现出明显的溶剂化效应;在同一溶剂中,随着染料结构中Br原子取代基数目的增加,发射波长发生红移,吸收波长变化不大,摩尔消光系数逐渐增大,荧光量子产率逐渐减小,表现出明显的重原子效应.     

Adsorption behaviour of azo disperse dyes on polyurethane fibre

Adsorption isotherms of disperse dyes were measured and the surfaces of dyed polyurethane, cellulose diacetate and polylactic acid fibres were observed using a scanning electron microscope and compared. Obvious crystal growth of the dyes occurred on the surface of the polyurethane fibres. The maximum dye uptake on polyurethane fibres and the degree of crystal growth varied greatly with the dye type. Factors such as the dye affinity for the fibre, crystallisation properties and dye solubility in the dyebath affect the sorbed state of the dye on the fibre surface. A mechanism is proposed for crystal formation on the fibre surface during dyeing of polyurethane fibre with disperse dyes.     

Photoregulated sorption of dyes to polymers I. The effect of polymers on some photochemical properties of acid yellow 38

The effect of polymers [gelatin, dextran, poly(vinyl alcohol), polyvinylimidazoles] on the photochemical and thermal isomerization of the water-soluble bisazo dye, Acid Yellow 38, has been studied. The absorption spectrum curve of the cis AY38 isomer was obtained using the method of Fischer. We have shown that the rate of thermal cis–trans isomerization of AY38 is first order and independent of pH from 6 to 9. An activation energy of 84 ± 4 kJ mol^?1 has been calculated for this process. The effect of added polymers on the rate of this conversion is relatively small. The quantum yields for the trans-cis and cis–trans conversions have been estimated to be 0.15 ± 0.01 and 0.34 ± 0.03, respectively, for irradiation at 380 nm. Only polyvinylimidazoles were found to influence the behavior of the dye to any degree. For quaternized polyvinylimidazole the polymer/dye ratio determined solution turbidity, wavelength of maximum absorption, molar absorptivity, and the degree of conversion at photoequilibrium. The effect of polymer was interpreted in terms of increased dye/dye interactions due to high local concentration of the dye bound to polymer. The charge neutralization and crosslinking by the dye due to ionic interactions are seen to be the cause of polymer/dye complex precipitation. Precipitation occurs over a narrow [polymer]/[dye] ratio range.     

Dyeability of polyurethane nanofibres with disperse dyes

Nanofibres enjoy broad technical applications in filtration, medical, biosensing, functional, and high‐performance textiles. Recent trends/developments in nanofibre research have also focused on the coloration of nanofibres. In this context, polyurethane nanofibre webs, which have been commercially successful, were electrospun and dyed with a high‐energy‐level CI Disperse Red 167:1 dye and a low‐energy‐level CI Disperse Blue 56 dye by the pad‐dry‐cure method. The dyed polyurethane nanofibres exhibited good colour strength values with acceptable colour fastness. Results revealed that the high‐energy‐level dye produced slightly better colour strength than the lower‐energy‐level dye. Further, scanning electron microscopy images showed that the morphologies of dyed and undyed nanofibres were almost identical.     

Preparation and properties of maleimide capped polyurethane/allyl novolac resin AB crosslinked polymers

To improve the miscibility and tensile strength of the ABCPs material, we conducted a study in which maleimide end-capped polyurethane was prepared from the PU prepolymer and maleimide by reacting 4,4′-diphenylmethane diisocyanate (MDI) with poly(tetramethylene oxide) (PTMO), whose molecular weights were M_n=600∼700 (PA650), M_n=900∼1050 (PA1000) and M_n=1900∼2100 (PA2000). AB crosslinked polymers (ABCPs), synthesized from the PU prepolymer and the novolac resin, were studied. The study confirmed the occurrence of phase mixing. Further investigation through dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) revealed that the tensile strength and phase mixing were,improved.     

Synthesis, characterization and photophysical properties of benzil-labelled polymers for studies of diffusion-limited interactions by phosphorescence quenching

A new technique for synthesizing benzil-labelled polystyrenes has been developed. This new procedure has advantages over an older synthesis by Horie and Mita in that it involves fewer and less complicated synthetic steps. In addition, the new synthetic pathway should allow for labelling of different sites on the polymer chain and for labelling of different polymers such as poly(methyl methacrylate). The phosphorescence lifetime of terminally benzil-labelled polystyrenes in cyclohexane was found to be approximately 85–90 μs at 25°C with the concentration of benzil at 10⁻⁵ M and was independent of labelled polystyrene molecular weight and polystyrene concentration up to 150gl⁻¹. When used in phosphorescence quenching studies, these materials were found to exhibit non-single-exponential lifetimes in the presence of anthracene and azulene quenchers for a concentration of benzil label 10⁻⁴ M. An explanation for this anomalous behaviour and a technique for decoupling these decays into two lifetimes has been proposed. This technique should allow for the study of diffusion-limited interactions occurring in higher-molecular-weight polymer systems where the label concentration 10⁻⁴ M.     

Synthesis of novel multifunctional photostabilizers containing UVA and HALS moieties and their effects on polymers and dyes

Ultraviolet absorbers and hindered amine light stabilizers are two kinds of efficient photostabilizers, which have different mechanisms. It is possible to make a synergistic interaction if introducing these two types of photostabilizing fragments into one molecule. In this article, two novel multifunctional photostabilizers UVH‐1 and UVH‐2 containing UVA and HALS fragments were synthesized from a 2‐hydroxyphenylbenzotriazole compound (UV‐P). UVH‐1 was synthesized by a three‐step synthetic strategy via esterification, bromination, and amination. UVH‐2 was facilely synthesized by a one‐step three‐component Mannich reaction. The chemical structure of UVH‐1 and UVH‐2 were confirmed by Fourier‐transform infrared (FTIR), ¹H NMR, ¹³C NMR, and mass spectrometry. Both multifunctional photostabilizers UVH‐1 and UVH‐2 show good ultraviolet absorption performance and excellent light stabilizing effect when applied to photoprotection of dye, polyacrylonitrile, and polyurethane in the solution state, in which UVH‐1 shows better light stabilization performance even on polymers. It can be concluded that a combination of the HALS and UVA active groups can enhance the photoprotective effect on dyes and polymers and also increase the molecular weight of the additive to overcome escape of the photostabilizer from the polymer matrix. J. VINYL ADDIT. TECHNOL., 26:259–267, 2020. © 2019 Society of Plastics Engineers